<?php
class LtCaptcha
{
    public $configHandle;
    public $storeHandle;
    public $imageEngine;
    public function __construct()
    {
        if (!$this->configHandle instanceof LtConfig) {
            if (class_exists("LtObjectUtil", false)) {
                $this->configHandle = LtObjectUtil::singleton("LtConfig");
            } else {
                $this->configHandle = new LtConfig;
            }
        }
    }
    public function init()
    {
        if (!is_object($this->storeHandle)) {
            $this->storeHandle         = new LtStoreFile;
            $this->storeHandle->prefix = 'LtCaptcha-seed-';
            $this->storeHandle->init();
        }
    }
    public function getImageResource($seed)
    {
        if (empty($seed)) {
            trigger_error("empty seed");
            return false;
        }
        if (!is_object($this->imageEngine)) {
            if ($imageEngine = $this->configHandle->get("captcha.image_engine")) {
                if (class_exists($imageEngine)) {
                    $this->imageEngine       = new $imageEngine;
                    $this->imageEngine->conf = $this->configHandle->get("captcha.image_engine_conf");
                } else {
                    trigger_error("captcha.image_engine : $imageEngine not exists");
                }
            } else {
                trigger_error("empty captcha.image_engine");
                return false;
            }
        }
        $word = $this->generateRandCaptchaWord($seed);
        $this->storeHandle->add($seed, $word);
        return $this->imageEngine->drawImage($word);
    }
    public function verify($seed, $userInput)
    {
        if ($word = $this->storeHandle->get($seed)) {
            $this->storeHandle->del($seed);
            return $userInput === $word;
        } else {
            return false;
        }
    }
    protected function generateRandCaptchaWord()
    {
        $allowChars           = $this->configHandle->get("captcha.allow_chars");
        $length               = $this->configHandle->get("captcha.length");
        $allowedSymbolsLength = strlen($allowChars) - 1;
        $captchaWord          = "";
        for ($i = 0; $i < $length; $i++) {
            $captchaWord .= $allowChars[mt_rand(0, $allowedSymbolsLength)];
        }
        return $captchaWord;
    }
}
